FIELD OF THE INVENTION The present invention relates to an industrial robot comprising a manipulator, a control unit having means for automatically oper- ating the manipulator, and a portable operating unit having means for manually operating the manipulator.

The present invention also relates to an industrial robot system comprising a plurality of industrial robots each having a mani- pulator and a control unit having means for automatically oper- ating the manipulator, and at least one portable operating unit for teaching and programming the manipulators, which portable operating unit is adapted for wireless communication with the control units.

The present invention further relates to an operating unit for an industrial robot having a specified identity, a manipulator and a control unit for controlling the manipulator, the operating unit comprising means for manually operating the manipulator and means for communicating with the control unit.

The present invention further relates to a method for controlling an industrial robot, comprising a manipulator and a control unit for controlling the manipulator, with a portable operating unit for teaching and manually operating the manipulator.

The invention also relates to the use of an industrial for opera- tion control at a spot welding station.

A movable operating unit is generally denoted a teaching pen- dant, and is used for manually controlling the robot, for example to teach or program the robot to follow an operating path.

PRIOR ART Robots are used to carry out repetitious and precise tasks, such as welding and painting of components. The robots are pro- grammed to carry out a work or a work cycle along an operating path. In order to program or teach the robot its working cycle, the robot is manipulated to various positions along the desired operating path. These positions are stored as instructions in a memory in the control unit. Other information, such as desired robot movement velocity, may also be stored in the memory.

During operation of the robot, the program instructions are exe- cuted, thereby making the robot operate as desired.

Various devices used to facilitate the programming of robots are known in the art. For example U. S. Pat. No. 4,888,708 issued to Brantmark et al discloses a portable teach pendant, for teaching and manually operating the robot, by use of a joystick, a key- board, and a visual display unit. The keyboard has various func- tion keys which permit an operator to select different states for the control system. The teach pendant may for example be used for monitoring the robot program, changing certain variables in the program, starting, stopping and editing the program, and for manually moving the manipulator by use of the joystick. The op- erator is teaching the robot while watching the motion of the manipulator.

A robot can be operated in at least two modes: automatic and manual. The choice of mode, in which the robot shall operate, is made by switching a mode selector key on a control panel on the control unit. When the robot is in the manual mode, the teach pendant has the exclusive right to operate the robot and thus no other operating units are allowed to control the robot.

When the robot is in the automatic mode, some of the functions in the teach pendant are blocked, for example the functioning of the joystick.

The teach pendant disclosed in the above mentioned U. S. pat- ent is connected to the control unit via a flexible cable or wire.

There are many problems related to having a cable between the control unit and the teach pendant, particularly when there are several robots arranged near each other in a robot line. The ca- ble between the teach pendant and the control unit has to be rather long and the risk for twisting the cables of the robots is considerable. Neighboring robots could also have their cables twisted with each other and thus it is sometimes difficult to know to which robot a certain teach pendant belongs. There is also a risk for breakage of the cables resulting in loss of communica- tion between the teach pendant and the control unit.

From the German patent No. DE 195 36 293 it is known to use a wireless link for exchange of information between the teach pendant and the robot. One advantage with a wireless connec- tion between the robot and the teach pendant is the possibility of using the same teach pendant for several robots. Accordingly, the teach pendant does not belong to a certain robot, and may be used together with any of the robots in a robot cell.

Robots are usually placed in robot cells in order to facilitate the automation of a complex series of actions. When one of the ro- bots in a robot cell is to be placed under manual control using a wireless teach pendant, it is important that the teach pendant is communicating with and controlling the correct robot. It must be possible to ensure correct association between the wireless teach pendant and the control unit. Otherwise, there is a risk for personal injury, should the operator believe that he is operating a certain robot but is instead operating another robot in the cell.

Thus, a problem arising when using a teach pendant not physi-

cally connected with the robot, is how to ensure that the correct robot is connected with the teach pendant.

Another problem with wireless communication between the robot and the teach pendant is the functioning of the emergency stop button on the teach pendant when the teach pendent is not con- nected with any robot. For safety reasons it is required that a visible emergency stop button stops the robot at any time the button is pushed. Accordingly, the teach pendant is not allowed to have a visible emergency stop button when it is not con- nected to any of the robots.

SUMMARY OF THE INVENTION The object of the present invention is to provide an industrial robot having a portable operating unit which overcomes the pro- blems mentioned above and in particular the problem to ensure that the correct robot is connected with the portable operating unit.

This object is achieved by means of the initially defined indus- trial robot, characterised in that device, characterised in that it comprises a movable key device carrying information about the identity of the robot and said portable operating unit comprising a member for receiving said movable key device and means for reading the robot identity from the key device. The key device is provided with information about the identity of the robot to which the operating unit shall be connected. By physically moving the key device to the operating unit, and transferring the robot iden- tification to the operating unit, it is possible to ensure that the operating unit knows which robot it shall be connected to. If the operating unit is connected to the robot through a cable, it is possible to compare the identity from the key with the identity of the connected robot. If the identities are identical, the operating unit are enabled for operation, otherwise the operating unit is blocked from operation.

According to a further embodiment of the invention, the portable operating unit and the control unit are adapted for wireless com- munication with each other. The invention is particularly useful in connection with a wireless operating unit. For ensuring that the operating unit is associated with a certain robot, having a specific identity, the identification of the robot is transferred to the operating unit by physically moving the key device to the operating unit. Accordingly, it is possible to ensure correct as- sociation between the wireless operating unit and the robot.

According to an embodiment of the invention, the robot com- prises a second member for receiving the movable key device and said second receiving member being located at or in con- nection with the control unit of the robot. While the robot is not operated by the operating unit, the key device is returned to the robot, preferably to the controller or to a location close to the controller. Thus, it is easy for an operator to visually notice to which robot the key device belongs and mistakes due to the op- erator taking the wrong key device are prevented.

According to a further embodiment of the invention, the portable operating unit comprises means for displaying the identity of the robot. To further prevent mistakes due to uncertain identification of which robot the operating unit is operating at the moment, the identity of the robot associated with the operating unit is dis- played on the operating unit.

According to a further embodiment of the invention, the portable operating unit comprises means for sensing the presence of the key device and means for enabling manual operation of the ma- nipulator in presence of the key device in the operating unit. The control unit comprises means for sensing the presence of the key device and means for enabling automatic operation of the manipulator in presence of the key device. In this embodiment the key device can also functions as a switch between automatic

and manual mode of operation of the robot. By moving the key device to the operating unit, the robot is brought to operate in the manual mode and by moving the key device back to the controller the robot is brought to operate in the automatic mode.

According to a further embodiment of the invention, the portable operating unit comprises means for establishing a communica- tion with the control unit of the identified robot. A communication between the operating unit and the control unit of a robot can be established as soon as the operating unit has received informa- tion about the identity of the robot to which it shall be associ- ated. Since the identification of the robot is transferred by the key device, no communication could be established until the key device is present in the operating unit. Accordingly, when a communication is established with the control unit, the control unit knows that the operating unit has received the key device.

According to a further embodiment of the invention, the commu- nication between the portable operating unit and the control unit is carried out via a base station and the movable key device is adapted for carrying information about the address of the base station. To facilitate the establishment of the communication be- tween the portable operating unit and the control unit, the ad- dress of the base station is transferred to the operating unit through the key device. For a robot cell, having several robots connected to a base station, the number of key devices could be the same as the number of robots in the cell. The key devices will all have the same base station address, but different robot identities.

According to a further embodiment of the invention the control unit comprises means for measuring the time elapsed between the point of time when the key unit is removed from the second receiving member until communication is established between the portable operating unit and the control unit. Preferably, the control unit comprises means for comparing said time with a

predetermined maximum time and for emergency stopping the manipulator depending on said comparison. For the purpose of detecting a loss of the key device, a timer is started upon re- moval of the key device from the control unit. The timer is stopped when the key device is received by the operating unit and the communication is established. If the time exceeds a predetermined maximum time, an emergency stop of the robot is executed.

According to a further embodiment of the invention, the control unit comprises means for determining whether the key device received by the second receiving member carries the same identification as the robot. A problem associated with having a movable key device is the risk for returning the key device to the wrong robot. This problem is solved by providing the control unit with means for checking the identity of a received key device.

According to a further embodiment of the invention, the key unit comprises an emergency stop button. With a movable key de- vice provided with an emergency stop button, it is ensured that the operating unit will always have a working emergency stop button when the robot is controlled by the operating unit.

According to a further embodiment of the invention, the movable key device comprises an electronic hardware device, for exam- ple an information storage device. According to a further em- bodiment of the invention, the movable key device comprises a processor.

According to a further embodiment of the invention, the control unit comprises means for detecting lack of robot identity in the key device and means for transferring the identity of the robot to the key device. Preferably, the control unit also comprises means for detecting lack of robot identity in the control unit itself and means for transferring the identity of the robot from the key device to the control unit.

A further object of the invention is to provide an industrial robot system having a plurality of robots and at least one wireless op- erating unit which could operate anyone of the robots, if correct- ly associated with it, which robot system overcomes the pro- blems mentioned above and in particular the problem in connec- tion with the functioning of the emergency stop button. This ob- ject is achieved by the robot system as defined in claim 17.

Another object of the invention is to provide a portable operating unit overcoming the problem to ensure that it is connected with a certain robot, having a specified identity. This object is achieved by the operating unit as defined in claim 21.

Another object of the invention is to provide a method for con- trotting an industrial robot with a portable operating unit, which method solves the problem to ensure that the correct robot is connected with the portable operating unit. This object is achieved by the method of the invention as defined in claim 25.

Many of the above mentioned means are effectuated by soft- ware instruction run on a processor in the operating unit or a processor in the control unit.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained more closely by the de- scription of different embodiments thereof and with reference to the appended drawings.

Fig. 1 is a perspective view of an industrial robot according to one embodiment of the invention, comprising an operat- ing unit adapted for wireless communication with a con- trol unit of the robot.

Fig. 2 is a block diagram of the operating unit according to one embodiment of the invention.

Fig. 3 is a block diagram of the control unit of an industrial ro- bot according to one embodiment of the invention.

Fig. 4 shows an industrial robot system according to one em- bodiment of the invention, comprising an operating unit in wireless communication with the robots.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Figure 1 shows an industrial robot according to the invention, comprising a portable operating unit 1 and a control unit 2 cou- pled for transmitting data via a communication cable or a link to a manipulator 3. The operating unit and the control unit are ad- apted for radio communication with each other. The control unit 2 is capable of processing and outputting data received from the operating unit. The operating unit 1 comprises a body 4, a dis- play screen 5, a set of function keys 6, and a joystick 7. The function keys 6 permit an operator to select various states for the control system. The joystick is used for controlling the movement of the manipulator when the robot is manually oper- ated and could be used as a mouse. The operating unit 1 further comprises an antenna 9 for radio communication with the control unit 2 and a slot 8 adapted for receiving a key device 10. In this embodiment of the invention the key device is a card having an electronic hardware device 16 including a memory or a register adapted for storing information about the identity of the robot, to which the key device belongs. The control unit 2 comprises an operator panel 13 having keys for setting the control unit, an emergency stop button 14 and an slot 15 adapted for receiving the key device 10.

Figure 2 shows the operating unit 1 having received the movable key device 10 through the slot 8. A sensor member 20, posi- tioned inside the operating unit 1, is adapted for sensing the presence of the key device 10 in the operating unit 1 and read- ing the information about the robot identity from the hardware device 16. This information is transmitted via a bus interface 21 to a data bus 22. The operating unit 1 further comprises a proc- essing unit 23 adapted for processing data programs for control- ling the function of the operating unit, a memory 24 for storing the data programs and the information about the robot identity, interface means 25 for coupling input and output signals be- tween the data bus 22 and the display screen 5, the function keys 6 and the joystick 7, and a coupling element 26 for con- verting and coupling data between the antenna 9 and the data bus 22.

Figure 3 shows the control unit 2 having received the movable key device 10 through the slot 15. A sensor unit 30 is adapted for sensing the presence of the key device 10 in the control unit 2 and reading the information about the robot identity from the hardware device 16 to the data bus 32 via a bus interface 31.

The control unit 2 further comprises a processing unit 33, a memory 34 for storing data programs and parameters, a first interface means 35 for transmitting input and output signals be- tween the data bus 32 and the operator panel 13, a coupling element 36 for converting and coupling data between an an- tenna 39 and the data bus 32, and a second interface means 38 for transmitting data and control signals between the data bus 32 and the manipulator. The control unit 2 also includes a timer unit 37, discussed below.

When the operating unit 1 is not used, the key device 10 is po- sitioned in the control unit 2. If an operator decides to use the operating unit, he moves the key device 10 to the operating unit 1. The sensor member 20 senses the presence of the key device 10 and reads the information about the robot identity from the

hardware device 16 and transmits it, to the processor unit 23 via the data bus 22. When the processor unit has received the in- formation about the robot identity, it establishes a radio contact with the control unit 2 of the identified robot via the coupling element 26 and the antenna 9.

When the operating unit 1 is not to be used, the key device 10 is returned to the control unit 2 and remains there until the next time the operating unit 1 is to be used. When the sensor mem- ber 30 in the control unit 2 has sensed the presence of the key device 10, it transmits the information about the robot identity from the hardware device 16, via the data bus 32, to the proces- sor unit 33. When the processor unit 33 has received the infor- mation about the robot identity, it compares it with a stored ro- bot identity, for the purpose of checking that the received key device is the correct one, belonging to the robot. If the identities are not the same, the control unit will not accept receiving the key device and will generate an alarm signal.

For the purpose of detecting a loss of the key device 10, the timer unit 37 is started when the key device 10 is removed from the control unit 2 and is stopped when the key device is re- ceived by the operating unit 1 and the communication is estab- lished. When the timer runs out, i. e. when the time elapsed ex- ceeds a predetermined maximum value, an emergency stop is executed or any other action is taken.

The robot may be operated in an automatic or a manual mode.

Normally, the robot is in the automatic mode during work and in the manual mode during teaching. In an embodiment of the in- vention, the switching between the automatic and the manual mode could be effectuated by moving the key device from the control unit to the operating unit and vice versa. Accordingly, upon sensing the presence of the key device in the control unit, the robot is operated in the automatic mode, i. e. the robot is un- der automatic control, and upon sensing the presence of the key

device in the operating unit, the robot is operated in the manual mode, i. e. the robot is controlled by the operating unit.

Figure 4 shows a robot cell having six robots, each comprising a manipulator 3a-3f and a control unit 2a-2f. Each robot can be controlled via a portable operating unit 1. The control units 2a-2f and the operating unit 1 are adapted for being in radio commu- nication with each other via a base station 40. For activating the operating unit 1 it needs to have the address of the base station 40 and the identity of the robot to which it shall be connected.

This is done by moving the key device from the selected robot to the operating unit 1. Beside the robot identity, the hardware unit 16 comprises the address of the base station. The robot identity includes the network address of the robot to be controlled by the operating unit. The six key devices 10a-10f have the same base station address but different robot identities. In the example shown in figure 4, the robot comprising controller 2d is selected for being controlled by the operating unit 1. Thus, the key device 10d is moved to the operating unit 1.

Each of the robots in the cell has a key device. If the cell com- prises more than one operating unit 1, the key devices can be used in any of the operating units, but the control units will only accept one unique key device. The linking between a robot and an operating unit is done by use of the movable key device. Any number of operating units can be active in the cell, but the only operating unit able to manipulate the robot is the one in posses- sion of its key device.

Upon return of the key device 10d to the control unit 2d, the op- erating unit 1 will send a message to the control unit informing it about the fact that the key device has been removed from the operating unit. This will stop the manipulator and start the timer in the control unit. The timer is stopped when the control unit has received the key device. If the transfer time exceeds a pre- determined value, the emergency stop will be activated. If it is

not possible to communicate with the control unit when the key device is removed from the operating unit, the manipulator is stopped from the moment the communication is broken, until the control unit has received the key device.

As long as the key device is not present in the control unit, the communication with the operating unit is supervised and the control unit will emergency stop the robot if the communication is broken and the key device is not returned within a predeter- mined time interval. The communication may be broken, for ex- ample if the operating unit leaves the radio coverage area.

Thus, if the key device is still in the operating unit when the op- erating unit leaves the radio coverage area, the robot will be emergency stopped.

In another embodiment of the invention, the key device com- prises a first part fixedly arranged in the control unit and a sec- ond movable part. The second movable part is used for mes- sage encryption and the first part is used for message decryp- tion.

In an embodiment of the invention, the key device comprises an emergency stop button. When the key device is received by the operating unit or by the control unit, the emergency stop button is enabled and will trigger an emergency stop if activated.

The present invention is not limited to the embodiments dis- closed but may be varied and modified within the scope of the following claims. For example, the means for carrying informa- tion about the identity of the robot could be implemented in a number of different ways, such as a physical key device, mag- netic means, a bar-code or any other visible means. The means for reading the robot identity from the key device could for ex- ample be a mechanical, magnetic, an electromagnetic or an op- tical reading means. The electronic hardware device in the key device is preferably comprising a processor and software in- structions.